Sept. 9, 1993. 9:07 a.m. A U- Haul bobtail truck backed up to the loading dock at Wyle Laboratories, an electronics company in Santa Clara.

With the precision of a commando team, six men leaped out. They wore blue coveralls and nylon stockings over their heads, except for one who had a cloth mask. Two carried handguns.

Four of the men dashed into a caged area where computer chips are held for shipment. One man stood guard outside, and the sixth ran through the shipping area ordering employees to the floor.

Within seconds, the men stuffed $739,488 worth of state-of-the- art Intel 486 microprocessors into a bag and fled in the truck.

One employee told police the thieves seemed to know exactly where to go and moved so quickly they were gone before most employees knew what had happened.

Minutes later, police found the U-Haul a few blocks away, its engine still running, along with discarded coveralls, masks and guns.

Investigators later linked the spectacular robbery to a visit a month earlier from a man who appeared to be Middle Eastern. He said he wanted to buy $5 million worth of chips for the United Arab Emirates and was given a tour of the plant.

The robbery, which remains unsolved, sent shock waves through Silicon Valley. Until then, most high-tech robberies had been confined to small operators; Wyle is a $1 billion company. Its mammoth Santa Clara plant dominates a busy intersection.

That holdup and others that followed sent a chilling message to the computer industry: High-tech robbery is big business.

In 1993, the Chubb Group of Insurance Companies, which says it covers about half of Silicon Valley, paid out less than $3 million in claims related to high-tech thefts. The payments skyrocketed to more than $15 million in 1994 and will likely exceed that this year.

The insurance group estimates the illicit trade in computer components is an $8 billion business.

Robberies are becoming more frequent because the rewards are huge. The average take is $450,000, according to the FBI.

"If we had bank robberies of that magnitude, you'd probably find the United States Marine Corps and most of the Army deployed around our banking institutions," said Colin Elrod, investigations manager for Amdahl Corp., a Sunnyvale computer company.

The robberies are usually well- planned, sometimes based on inside information supplied by employees or gleaned from careful surveillance.

"It's easier to pull off than a bank robbery and just as profitable as drug dealing," said federal prosecutor Steven Gruel of the Justice Department's Organized Crime Strike Force in San Francisco. "And the punishment generally isn't as severe."

High-tech thieves typically target microprocessors, the tiny silicon chips that constitute the brains of personal computers, controlling all their functions. They are small and expensive, and demand for them is great, all of which make it easy to slip them into the legitimate market.

A top-flight Pentium chip is slightly bigger than a postage stamp and sells for just under $700. A shoe box full is worth nearly $35,000.

Typically, those who traffic in these chips have "one foot planted firmly in the business world and the other foot planted in the criminal world," said Sergeant Ray Smith of the Santa Clara Police Department.

Stolen high-tech equipment may change hands a half-dozen times within 72 hours, leaving the trail cold by the time detectives get the case. It can find its way quickly into the mainstream market.

Some stolen chips are shipped overseas, and authorities say they sometimes are used in other countries to build computers that are then sold back to the United States.

In 1992, the Santa Clara Police Department arranged a deal involving $1.6 million in purportedly stolen Intel chips, implicating salesmen for U.S. companies, a salesman for a Taiwanese company and the representative of an Argentine computer distributor.

Shih came to a meeting at the Biltmore Hotel in Santa Clara with shipping boxes, tape and a leather pouch containing $250,000 in cash and cashier's checks.

"I was sitting there in the hotel room talking to him for 3 1/2 hours, and all I could think of is this guy is the vice president of a Taiwanese computer company," recalled Kerby, who had an undercover role in the operation.

The Wyle robbery also heralded a new boldness by computer chip thieves. Big profits have attracted criminals more willing to use violence. -- On February 2, robbers shot a security guard and tied up the wounded man while they ransacked a Stratacom Corp. plant in San Jose. -- On May 16, as many as 14 robbers pulled off the largest high-tech heist in history at Centon Electronics in Irvine, making off with $9.9 million in components. As they tied up one employee and ordered him not to call police, they took his wallet and told him they knew where he lived. -- On July 30, a security guard, Nemesio Ngo Ganan III, 23, was beaten and then shot execution-style at Far Western Graphics, a small Santa Clara firm. Police have not caught the thieves or recovered the computer equipment and pick- up truck that were stolen.

The violence of these recent crimes has forced the computer industry to beef up security.

Many companies now require employee badges and have installed security entrances that make them seem more like Cold War defense plants.

A month after the Wyle robbery, Intel Corp., the world's largest chipmaker, announced it would begin stamping its most expensive chips with serial numbers to make them more easily traceable.

Intel, along with other big computer companies, has furnished millions of dollars in chips and components used as bait in sting investigations, which are law enforcement's principal weapon against the robbers.

In 1992, the FBI and police departments in high-tech meccas such as San Jose and Santa Clara began a series of stings as sophisticated and audacious as the criminals they sought to ensnare.

The central figure in one series of these stings was Larry Tran, a 39-year-old Vietnamese immigrant living in San Jose. An FBI affidavit said he was making $1 million a year trafficking in stolen computer chips. Following his trail for three years, investigators from the Santa Clara Police Department got an inside view of Silicon Valley's black market for stolen chips -- from those who commit the robberies, to the brokers who traffic in stolen goods, to seemingly legitimate computer retailers who sell them to the public.

Tran and two other men operated a company called Computer Storage Peripherals in a small shop off the Montague Expressway, where they supposedly refurbished hard disks. Its real business was the illegal trade of stolen computer equipment, police say.

In the sting, an undercover detective tried to make a sale to one of Tran's associates, showing him a Ryder truck jammed with $16 million in borrowed computer parts.

Tran and his friends couldn't come up with the $2.5 million asking price, but agreed to pay $250,000 for some of the merchandise.

Tran arrived to take the delivery with two bodyguards. His own countersurveillance team was posted around the grounds of the hotel where the sting took place.

Tran ordered his bodyguards to peer in the windows of a van parked nearby, but they failed to notice the SWAT team hiding inside.

After his arrest, a search of Tran's shop and a storage locker turned up $1.5 million in stolen goods, including $500,000 in computer boards stolen from Sun Microsystems. Tran's firm's bank account showed $1 million in business transactions during the previous six months, almost none of it legitimate, Kerby said.

While free on bail, Tran continued to traffic in stolen chips and was caught in another sting, this one conducted by the FBI.

Between February and July 1994, Tran and his associates bought 1,377 chips from an undercover officer, according to an FBI affidavit.

In February, Tran, already sentenced to seven years in state prison for receiving stolen computer components, pleaded guilty in federal court to conspiracy to receive stolen goods and agreed to testify against former associates.

Before Tran's second arrest and subsequent guilty plea, he unwittingly gave investigators clues leading to one more sting, this one aimed at Lawrence Wong and his San Jose computer store, Prestige Computer.

Wong and his associates were arrested in May for allegedly receiving stolen goods and for conspiracy to commit robbery.

Richard Bernes, who heads the high-tech squad in the FBI's San Jose office, said the stings are having the desired effect and the number of big computer-chip robberies dropped off after Wong's highly publicized arrest.

The stings are expensive and time-consuming, but effective: No thief can be sure his buyer or supplier isn't an undercover agent.

"We want that to be a big question mark in their minds," Bernes said with a wry smile.